Self-orienting casters, particularly of the so-called twin type, constituted by two wheels mounted so that they can rotate about a shaft, are known. The shaft is supported in a seat that is formed in a supporting structure that lies between the wheels and often comprises a sort of semi-cylindrical housing that covers the wheels in an upper region.
A vertical cylindrical recess is formed in the supporting structure, is open upward and axially offset with respect to the shaft, and acts as a rotation seat for a vertical pivot for the self-orientation (pivoting) of the caster, which is designed to be inserted and retained in a seat of the piece of furniture on which the wheel is to be fitted.
Self-orienting casters of the described type have the drawback that the pivot for self-orientation of the caster can often cause excessive and unpleasant noise, particularly when the caster runs over a rough surface or if the seat of the piece of furniture intended to receive the pivot is formed inside a metallic body. This is observed especially in chairs or armchairs that are provided with a metallic pedestal with radial arms, in which the casters are fitted at the ends of the arms. This drawback, which is present even with new casters, due to the inevitable plays of the pivots in respective recesses of the pedestal, is increased when the plays, due to use, tend inevitably to increase.